This invention relates generally to nuclear reactors, and more particularly to control rod drive system branch amplifier cards.
A reactor pressure vessel (RPV) of a boiling water reactor (BWR) typically has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A top guide typically is spaced above a core plate within the RPV. A core shroud, or shroud, typically surrounds the core and is supported by a shroud support structure. Particularly, the shroud has a generally cylindrical shape and surrounds both the core plate and the top guide. There is a space or annulus located between the cylindrical reactor pressure vessel and the cylindrically shaped shroud.
The reactor core is formed from a plurality of fuel elements. The fuel elements are grouped together at fixed distances from each other in a fuel bundle. A sufficient number of these fuel bundles are combined to form a reactor core capable of a self-sustaining chain reaction. Neutron-absorbing control rods are inserted into the core to control the reactivity of the core. The reactivity of the core can be adjusted by incremental insertions and withdrawals of the control rod.
Each control rod is housed within a vertical guide tube that ensures the vertical orientation and motion of the control rod. The control rod is moved using a control rod drive mechanism that is at least partially housed in a stub tube that also serves to support the base of the guide tube. A rod drive control system controls a hydraulic control unit (HCU) that causes the control rod drive mechanism to move the control rod, either inserting or withdrawing the rod from the fuel bundle. The HCU includes transponder cards that control the solenoids in the HCU.
Because the control rods are the primary means for regulating reactor output, it is essential that the control rod drives remain fully functional. The control rod drive system is designed to shut down and prevent movement of all control rods whenever one of the circuit boards that control the insertion or withdrawal of the control rods is determined to be defective. This requires immediate attention of plant personnel to replace the defective electronics so that the HCU can become fully operational. No control rod movement is possible until the defective circuitry is replaced.
In one aspect, a branch amplifier card for a nuclear reactor control rod drive control system is provided. The control system includes a control processor, a plurality of transponder cards arranged in clusters with each cluster under the control of a branch amplifier card. The branch amplifier card is configured to receive commands from the control processor, send the converted commands to transponder cards under the control of the branch amplifier card and to a downstream branch amplifier card, receive an acknowledge word from transponder cards under the control of the branch amplifier card, add AC voltage threshold level information about the transponder cards under the control of the branch amplifier card to the acknowledge word, permit transponder trouble information attached to the acknowledge word to remain in the acknowledge word, and resend the acknowledge word including the transponder trouble information to an upstream branch amplifier card.
In another aspect, a nuclear reactor control rod drive control system is provided. The nuclear reactor includes a plurality of control rods. The control system includes a control processor, a plurality of control rod drives with each control rod drive configured to connect to a control rod, and an hydraulic control unit connected to each control rod drive with the hydraulic control unit including a transponder card, and a plurality of branch amplifier cards operationally connected to the control processor and to each other. Each branch amplifier is operationally connected to and controlling a cluster of transponder cards. The branch amplifier card is configured to receive commands from the control processor, send the converted commands to transponder cards under the control of the branch amplifier card and to a downstream branch amplifier card, receive an acknowledge word from transponder cards under the control of the branch amplifier card, add AC voltage threshold level information about the transponder cards under the control of the branch amplifier card to the acknowledge word, permit transponder trouble information attached to the acknowledge word to remain in the acknowledge word, and resend the acknowledge word including the transponder trouble information to an upstream branch amplifier card.
In another aspect, a nuclear reactor is provided that includes a reactor pressure vessel, a reactor core located inside the reactor pressure vessel, and control rod drive control system. The core includes a plurality of fuel assemblies and a plurality of control rods. The control rod drive system includes a control processor, a plurality of control rod drives with each control rod drive connected to a control rod, an hydraulic control unit connected to each said control rod drive, and a plurality of branch amplifier cards operationally connected to the control processor and to each other. The hydraulic control unit includes a transponder card. Each branch amplifier is operationally connected to and controlling a cluster of transponder cards. The branch amplifier card is configured to receive commands from the control processor, send the converted commands to transponder cards under the control of the branch amplifier card and to a downstream branch amplifier card, receive an acknowledge word from transponder cards under the control of the branch amplifier card, add AC voltage threshold level information about the transponder cards under the control of the branch amplifier card to the acknowledge word, permit transponder trouble information attached to the acknowledge word to remain in the acknowledge word, and resend the acknowledge word including the transponder trouble information to an upstream branch amplifier card.